JP2699158B2 - Curable composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel siloxane-modified polyester resin useful for forming a magnetic layer of a magnetic recording medium.
It relates to curable compositions that use.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media used for audio equipment, computers and the like are obtained by forming a magnetic layer composed of magnetic particles and a binder resin on a non-magnetic support such as a polyester film. Such a magnetic layer is formed by applying a dispersion of magnetic particles dispersed in a medium containing a binder resin to a support. Although various physical properties are required for the magnetic layer, a particularly important required property is a good running property of the magnetic recording medium.
Therefore, it is strongly required that the coefficient of friction between the recording head and the magnetic recording medium is low. Such a level of the friction coefficient is mainly determined by the binder resin used for forming the magnetic layer. Conventionally, as a binder resin, a vinyl chloride resin, a polyurethane resin, a polyester resin, a nitrocellulose resin, an epoxy resin and the like have been used alone or in combination.

[0003]

The friction coefficient of the conventionally used binder resins as described above is generally 0.4 or more, and a magnetic recording medium formed from these binder resins is used for video tapes and audio tapes. When the tape is used as a tape, the slipperiness of the tape is insufficient. Is causing the out. As a method of solving such a cause and reducing the friction coefficient of the magnetic recording medium, a method of adding a lubricant such as a fatty acid, a wax, or a silicone oil to the magnetic layer has been performed. The method has another disadvantage in that the lubricant added to the magnetic layer bleeds out to the surface of the tape and causes clogging of the recording head. As a method of solving the above disadvantages, a resin having a low coefficient of friction as a binder resin itself,
For example, a method using a polyurethane resin having a siloxane bond in the molecule has been proposed (for example, JP-A-57-176535, JP-A-59-94237, and JP-A-5-94237).
Nos. 9-5421, 58-218034, 58-2
No. 22436, No. 59-11535, No. 59-826
See No. 36 publication. ). According to such a method, a magnetic layer having a relatively low coefficient of friction can be formed. However, it is difficult to sufficiently react the polyurethane resin having the siloxane bond, and it is difficult to obtain a binder resin having a constant quality. However, various problems are caused by the high price and unreacted silicone compound.

The inventor of the present invention has intensively studied to solve the above-mentioned drawbacks of the prior art and to develop a novel binder resin which meets the above-mentioned demands. As a result, the inventors have developed a polyester resin modified with a specific siloxane compound. The use of a binder resin solves the above-mentioned drawbacks of the prior art, and hardens the polyester resin and the crosslinking agent.
The inventors have found that a magnetic recording medium having a low friction coefficient can be provided by using the agent composition, and completed the present invention.

[0005]

That is, the present invention provides a siloxane compound obtained by copolymerizing a siloxane compound having at least one group having active hydrogen bonded to a silicon atom via another atomic group with a lactone. has a lactone polyester segment on at least one end of the segment, a siloxane segment content of 10 to 80 wt%, characterized in that the molecular weight is comprised of a siloxane-modified polyester-based resin and the crosslinking agent is from 1,000 to 30,000 It is a curable composition.

[0006]

A polyester segment obtained by copolymerizing a siloxane compound having at least one group having active hydrogen bonded to a silicon atom via another atomic group with a lactone, whereby the siloxane segment and the lactone are subjected to ring-opening polymerization. Is obtained. This resin has a low coefficient of friction, Ri resin der siloxane compound does not bleed, containing the siloxane-modified polyester resin as a binder E resin
By forming the magnetic layer of the magnetic recording medium with the curable composition, a magnetic recording medium having a low coefficient of friction is provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention is described in more detail with reference to preferred embodiments. The siloxane-modified polyester resin used in the present invention has at least one group having active hydrogen bonded to a silicon atom through another atomic group.
It can be obtained by copolymerizing a siloxane compound having two or more siloxane compounds (hereinafter referred to as an active hydrogen group-containing siloxane compound) with a lactone. Preferred examples of the active hydrogen group-containing siloxane compound used in the present invention include, for example,
The following compounds are mentioned.

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020] The above epoxy compound can be used by reacting it with a polyol, polyamide, polycarboxylic acid or the like so as to have a terminal active hydrogen.

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0031]

[0032]

[0033]

[0034]

The siloxane compounds having an active hydrogen group as described above are examples of preferred siloxane compounds in the present invention, and the present invention is not limited to these examples. The compounds are currently commercially available and are readily available from the market, all of which can be used in the present invention.

In the present invention, the lactone compound to be copolymerized with the siloxane compound having an active hydrogen group is a lactone compound capable of forming a polyester by conventional lactone ring-opening polymerization, such as ε-caprolactone and δ-valerolactone. Thus, mono- or di-substituted derivatives of these alkyls, halogens, haloalkyls, alkoxys, alkoxyalkyls and the like can be used as well. Particularly preferred lactone compounds are ε-caprolactone and derivatives thereof.

The lactone is subjected to ring-opening polymerization using a compound having an active hydrogen such as a hydroxyl group as a polymerization initiator, whereby the compound and a polyester formed by ring-opening polymerization of the lactone are copolymerized to form at least one end of the compound segment. It is known that a block copolymer in which a lactone polyester segment is bonded to is obtained (see, for example,
9-207922). The copolymerization of the siloxane compound and the lactone compound is carried out by mixing the two and reacting them at a temperature of 150 to 200 ° C. for several hours to several tens of hours, preferably using a suitable catalyst under a nitrogen stream. Thus, a desired siloxane-modified polyester copolymer is obtained. Both can be reacted at any reaction ratio, but for the purpose of the present invention, it is preferable to carry out the reaction so that the siloxane segment accounts for 10 to 80% by weight in the obtained copolymer. If the amount of the siloxane compound used is too small, the slip properties and running properties of the finally obtained siloxane-modified polyester resin become insufficient, while if it is too large, the film-forming properties and coating of the obtained siloxane-modified polyester resin become insufficient. It is not preferable because the strength is reduced.

The copolymer obtained as described above contains the unreactive siloxane compound contained in the siloxane compound used as it is, and varies depending on the siloxane compound used and the copolymerization ratio. , Usually about 1.0 to 5% by weight of the copolymer. The impurities as described above are difficult to separate at the raw material stage, or in the present invention, are continuously or after the copolymerization at a temperature of about 100 to 250 ° C., preferably 10 mmHg, preferably under an inert atmosphere such as nitrogen gas. Can be easily removed by performing a reduced pressure treatment under a condition of 5 mmHg or less, and a polyester resin of the present invention substantially free of an unreacted siloxane compound can be obtained. In the present invention, the term "substantially not contained" means that the content of the unreacted siloxane compound is less than 1.0%.

As described above, the polyester resin used in the present invention is about 1,000 to 30,0 in consideration of usability.
The molecular weight is preferably about 00, and the molecular weight may be adjusted by using a known technique as it is. Further, the copolymer has a reactive hydroxyl group at a terminal and can be cross-linked (cured) by various cross-linking agents (curing agents). The polyester resin used in the present invention as it is, in addition to excellent slip, running properties, etc., can form a coating having excellent migration resistance, bleed resistance, etc. By cross-linking with a cross-linking agent, it is possible to obtain a cross-linked film having more excellent physical properties.

As the crosslinking agent used in the curable composition of the present invention, a compound containing two or more functional groups capable of reacting with the terminal hydroxyl group of the polyester resin, such as a polyisocyanate compound and a polyepoxy compound, may be used. If the terminal hydroxyl group is further modified with another functional group, it can be crosslinked by a crosslinking agent having a hydroxyl group, an amino group, an aldehyde group or the like. Particularly preferred crosslinking agents are polyisocyanate compounds.

As the polyisocyanate, any known polyisocyanate can be used. For example, preferred are 4,4'-diphenylmethane diisocyanate (MD
I), hydrogenated MDI, isophorone diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, There are m-phenylene diisocyanate and p-phenylene diisocyanate, and urethane prepolymers obtained by reacting these polyisocyanates with low molecular weight polyols or polyamines to form terminal isocyanates can also be used.

The hardener of the present invention crosslinked with a crosslinking agent as described above
The coating of the curable composition is a tough coating that is excellent in non-adhesiveness, lubricity, blocking resistance, etc., migration resistance, bleed resistance, and the like. Therefore, the curable composition containing the siloxane-modified polyester resin of the present invention can be used to form a magnetic layer of a magnetic recording medium such as a magnetic tape, and to form a back coat on the back surface thereof.
Layer formation , formation of heat transfer film, etc. , formation of heat-resistant lubricating layer to prevent sticking of thermal head, material for synthetic leather,
It is very useful as a fiber coating agent, a surface treatment agent, the formation of a release layer such as release paper, the production of paints and printing inks, and the like.

[0043]

Next, the present invention will be described more specifically with reference to Production Examples, Examples, Comparative Examples, and Evaluation Examples. In the description, parts and% are based on weight unless otherwise specified.

[0044]

In a reactor equipped with a stirrer, thermometer, nitrogen gas inlet tube and reflux condenser, ε-caprolactone 240
Parts, 100 parts of the amino-modified siloxane oil having the above structure (1) and 0.05 parts of tetrabutyl titanate were charged and reacted at 180 ° C. for 10 hours in a nitrogen stream. As the reaction proceeds, the viscosity of the reaction product increases. Thereafter, the reaction was continued at 180 ° C. under a reduced pressure of 5 mmHg for 1 hour to complete the reaction and completely remove the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound. The unreacted siloxane compound removed was 15 parts. The product obtained has a hydroxyl value of 1
6 is a waxy polysiloxane-polyester copolymer having a melting point of 72 ° C.

[0046]

In the same manner as in Production Example 1, 160 parts of ε-caprolactone, 140 parts of an amino-modified siloxane oil having the above structure (2), and 0.04 part of tetrabutyl titanate were charged, and 180 parts of 10 ° C
Allowed to react for hours. As the reaction proceeds, the viscosity of the reaction product increases. Thereafter, at 180 ° C. under reduced pressure of 5 mmHg,
The reaction was continued for a period of time to complete the reaction, and the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound were completely removed. The unreacted siloxane compound removed was 18 parts. The resulting product is a waxy polysiloxane-polyester copolymer having a hydroxyl value of 18 and a melting point of 76 ° C.

[0048]

In the same manner as in Production Example 1, 200 parts of ε-caprolactone, 160 parts of an alcohol-modified siloxane oil having the above structure (3), and 0.05 part of tetrabutyl titanate were charged, and 180 parts of nitrogen was fed. 1 at the temperature of ℃
The reaction was performed for 0 hours. As the reaction proceeds, the viscosity of the reaction product increases. Thereafter, the reaction was continued at 180 ° C. under a reduced pressure of 4 mmHg for 1 hour to complete the reaction and completely remove the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound. The unreacted siloxane compound removed was 18 parts. The obtained product is a waxy polysiloxane-polyester copolymer having a hydroxyl value of 12 and a melting point of 78 ° C.

[0050]

In the same manner as in Production Example 1, 180 parts of ε-caprolactone, 160 parts of an alcohol-modified siloxane oil having the above structure (4) and 0.04 part of tetrabutyl titanate were charged, and 180 parts of 1 at the temperature of ℃
The reaction was performed for 0 hours. As the reaction proceeds, the viscosity of the reaction product increases. Thereafter, the reaction was continued at 180 ° C. under a reduced pressure of 3 mmHg for 1 hour to complete the reaction and completely remove the non-reactive siloxane compound and unreacted substances contained in the raw material siloxane compound. The removed unreacted siloxane compound was 16 parts. The obtained product is a waxy polysiloxane-polyester copolymer having a hydroxyl value of 14 and a melting point of 75 ° C.

Examples 1 to 4 Using the copolymers obtained in Production Examples 1 to 4, coating materials for a magnetic layer of a magnetic recording medium were prepared with the following composition. Co-containing Fe ₂ O ₃ 100 parts Polyester type polyurethane resin (35% solution) 54 parts 35% methyl ethyl ketone solution of copolymer 20 parts Lecithin (dispersant) 1 part Carbon black 5 parts Nitrocellulose 6 parts Methyl ethyl ketone 270 parts The mixture was mixed and kneaded in a ball mill for 50 hours. Further, Coronate L (manufactured by Nippon Polyurethane Co., Ltd .: N
CO% = 13.5, 8 parts of an adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate) were added,
The mixture was further kneaded for 3 hours, and the kneaded product was passed through a filter to obtain a dispersion of magnetic particles.

Each of the dispersions was applied to a polyester film having a thickness of 15 μm by a reverse roll coater so as to have a thickness of 5 μm. After the solvent was dried, the surface was processed by a super calender roll. Then, the magnetic recording medium was cut into a predetermined width to obtain a magnetic recording medium using the copolymer of the present invention. Table 1 shows the results of examining the performance of these magnetic recording media.
Were obtained. The coefficient of friction (A) is a value (μk) measured between the magnetic layer and the support (base film). The other performances were subjected to a mounting test as a video tape, The squealing of the tape (B), the lateral fluctuation of the jitter (C), the turbulent winding state (D) during fast-forwarding of the tape, and the abrasion state (E) of the magnetic layer were observed. The comprehensive evaluation is shown in (F).

Comparative Examples 1 to 3 A coating material for a magnetic layer of a magnetic recording medium was prepared in the same composition as in Examples 1 to 4. The binder resin of Comparative Example 1 was prepared by adding 150 parts of polybutylene adipate having a hydroxyl group at a terminal of 2,000, 20 parts of 1,3-butylene glycol and 52 parts of tolylene diisocyanate to methyl ethyl ketone 4
A polyester resin obtained by an addition reaction in 12 parts and used as a polyester resin solution (solid content 35%) having a viscosity of 200 poise / 20 ° C. The binder resin of Comparative Example 2 is a vinyl chloride / vinyl acetate / vinyl alcohol copolymer resin (S-LEC A: manufactured by Sekisui Chemical Co., Ltd.)
Used as a 35% solution of methyl ethyl ketone. The binder resin of Comparative Example 3 was a butyral resin (Elex B: manufactured by Sekisui Chemical Co., Ltd.)
% Solution. Magnetic recording media were formed and evaluated in the same manner as in Examples 1 to 4. Table 1 shows the results.

[0055]

[Table 1]

[0056]

According to the present invention as described above , the low friction coefficient
Comprising a siloxane segment obtained by copolymerizing a siloxane compound having an active hydrogen group and a lactone having migration resistance and bleeding resistance, and a siloxane-modified polyester resin having a lactone polyester segment, and a crosslinking agent. A curable composition is provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication // C09D 5/23 C09D 5/23 G11B 5/702 G11B 5/702 (72) Inventor Katsumi Kuriyama 1135-1 Kuri Shimoma, Koshigaya City, Saitama Prefecture (56) References JP-A-2-228323 (JP, A) JP-A 1-299819 (JP, A) Patent 2537395 (JP, B2)

Claims (1)

(57) [Claims] 1. A siloxane compound having at least one group having active hydrogen bonded to a silicon atom via another atomic group and a lactone, and a lactone polyester segment is provided on at least one end of the siloxane segment. Having a siloxane segment content of 1
0 to 80% by weight, molecular weight of 1,000 to 30,000
A curable composition comprising: a siloxane-modified polyester-based resin as described above; and a crosslinking agent.